Intumescent seals are a vital component of a building’s passive fire protection strategy, playing a key role in compartmentation and helping to prevent the spread of fire and smoke. Found around fire doors and sometimes windows, these seals expand when exposed to high temperatures, filling gaps and maintaining the fire-resistant barrier of walls, floors, and partitions.
But like any safety product, intumescent seals have a lifespan and require regular inspection and timely replacement to ensure they function properly in an emergency. In this guide, we’ll walk you through the lifecycle of intumescent seals, best practices for inspection and maintenance, and the signs that it’s time for a replacement.
What Are Intumescent Seals and How Do They Work?
Intumescent seals are typically installed around the edges of fire doors and fire-rated windows. When exposed to temperatures typically above 180°C, the material expands many times its original size, sealing gaps between doors and frames (or glazing and frames) to slow the passage of fire, smoke, and hot gases. This helps to:
- Maintain compartmentation during a fire
- Protect escape routes
- Limit fire spread and buy time for evacuation and firefighting efforts
In most buildings, intumescent seals work in tandem with fire-rated doors, glazing, and other fire-stopping measures.
The Lifecycle of Intumescent Seals
Although intumescent seals are durable and long-lasting, they are not permanent fixtures. Over time, they can become damaged, degrade due to environmental factors, or lose their effectiveness through regular use of doors or windows.
Expected Lifespan
With good care and under the right conditions, intumescent seals can last up to 20 years. However, the actual lifespan depends on:
- Environmental conditions (temperature fluctuations, humidity)
- Frequency of door or window use
- Quality of the installation and materials
- Damage from wear and tear or accidental impact
Even if a building has never experienced a fire, seals still need routine checks to ensure they’re ready to perform if required.
When to Inspect Intumescent Seals
Under UK fire safety regulations, including the Regulatory Reform (Fire Safety) Order 2005, responsible persons are required to maintain all fire safety equipment and measures, including intumescent seals.
Recommended Inspection Frequency
- Every 6 months as part of routine fire door inspections
- More frequently in high-traffic areas where doors are subject to constant use
- Immediately after any impact or suspected damage to doors or windows
- During fire risk assessments or compliance audits
If your building is subject to Fire Safety (England) Regulations 2023, and you manage high-rise residential buildings, quarterly inspections of common area doors are required.
What to Look for During Inspections
Inspecting intumescent seals is relatively straightforward but must be done carefully and thoroughly. Here’s what to check:
1. Physical Damage
- Cracks, splits, or breaks in the seal
- Sections of seal missing
- Tears from door impacts or general wear and tear
- Delamination, where the layers of material are separating
2. Detachment or Poor Adhesion
- Seals coming loose from the frame or glazing
- Gaps where the seal should form a tight fit
- Adhesive failure, where seals no longer sit flush against surfaces
3. Paint Over Seals
- Intumescent seals should never be painted over, as this can compromise their expansion capability
- Check for signs of paint build-up from previous redecorating
4. Excessive Wear or Compression
- Seals that are worn flat, frayed, or no longer springy
- Doors that don’t close properly because of deformed seals
- Over-compressed seals that have lost resilience
5. Environmental Damage
- Mould or moisture damage, particularly in humid environments
- Signs of UV damage on seals exposed to direct sunlight through windows
- Degradation due to chemical exposure in industrial settings
When to Replace Intumescent Seals
You should replace seals if:
- They show any of the damage outlined above
- They are missing entirely from the door leaf or frame
- The door set has been repaired or adjusted, requiring reinstallation
- The building undergoes a fire safety upgrade, and existing seals are non-compliant with current standards
- The manufacturer’s recommended lifespan has been reached (even if the seals appear in good condition)
Best Practices for Replacement
- Always use approved products that meet BS 476 Part 20/22 or BS EN 1634-1 standards
- Ensure seals are compatible with the fire door or window they’re installed on
- Follow the manufacturer’s instructions for installation
- Work with competent contractors who are experienced in passive fire protection installations
The Role of Combined Smoke and Intumescent Seals
Many modern fire doors are fitted with combined smoke and intumescent seals (often called cold smoke seals). These provide protection against smoke infiltration before the intumescent action begins at higher temperatures.
Additional Checks for Combined Seals
- Ensure the brushes or fins on the smoke seal are intact and not worn down
- Confirm they seal properly when the door is closed, with no visible gaps
- Replace damaged or missing smoke seals promptly, as smoke inhalation is one of the leading causes of fire-related fatalities
Why Intumescent Seal Maintenance Matters
Neglecting intumescent seals can compromise a building’s compartmentation strategy, allowing fire and smoke to spread more rapidly than designed.
Consequences of Failing Seals
- Breaches in fire resistance, putting lives at risk
- Non-compliance with UK fire safety regulations
- Potential fines or enforcement actions under the Fire Safety Order 2005
- Increased liability in the event of a fire-related incident
Maintaining seals is a critical part of any fire door inspection regime, and a minor oversight can have serious consequences.
Stay Ahead with Regular Inspections and Timely Replacement
Intumescent seals are a small but essential component of fire safety systems. Regular inspections, timely maintenance, and prompt replacement can be the difference between a contained fire and a catastrophic event.
Key Takeaways:
- Inspect intumescent seals at least every six months.
- Look for damage, detachment, compression, or signs of ageing.
- Replace any seals that are damaged, missing, or outdated.
- Ensure all seals are compatible and meet British Standards.
For advice or a consultation on your passive fire protection strategy, contact Martyn Young Fireproofing Consultancy today. We’re here to help you protect your building, its occupants, and ensure full compliance with UK fire safety laws.